As shown in FIGS. 1 & 2, a conventional lighter 1 comprises an idle wheel 11 rotatably pivoted on two ratchet arms on the top end of the lighter; and a tension spring below the idle wheel 11 acting upon a flint bar which biases against the coarse circumference of the idle wheel. Upon lighting up, the gas flowing out of a gas nozzle 13 may be ignited by rotating the idle wheel with the thumb to rub against the flint bar and simultaneously pressing down a pressing plate. Such a lighter is simple in structure, more convenient in usage, and, due to mass production, more popular in availability. However, it is also accompanied by with a risk that children playing with such a lighter may accidentally cause a fire.